By Kacey Cherry, Susannah Cullinane and Amanda Musa, CNN

Authorities are "making progress" in the investigation into the killings of four University of Idaho students found dead nearly 10 days ago, a state police spokesperson said Tuesday -- a day after the family of one of the victims grieved their loss at a memorial.

Stacy Chapin described her son Ethan Chapin as "one of the most incredible people you will ever know," ahead of a service Monday in Mount Vernon, Washington.

Chapin, 20, was found dead November 13 along with Kaylee Goncalves, 21; Xana Kernodle, 20; and Madison Mogen, 21. All four were discovered in a home near the University of Idaho campus in the city of Moscow after police responded to a call about an unconscious person, officials said. The victims had been stabbed to death, according to a county coroner.

After interviewing more than 90 people and receiving at least 700 leads, investigators believe they are "definitely making progress" in the case, State Police communication director Aaron Snell told CNN Tuesday. Authorities are also reviewing large files after asking the public for surveillance video from the area.

"This is a very large operation, a very large investigation and it's a very terrible crime," he said.

Ethan Chapin's family gathered before his funeral Monday to express thanks to their local community and extended family and friends, who she called "beacons of strength." She also expressed gratitude to strangers across the country who have reached out to express their support.

"Your outreach and kind words are profoundly touching. Please know we now consider all of you friends," Stacy Chapin said while flanked by family members.

Stacy Chapin also thanked the Moscow Police Department, saying its investigators "now carry the burden every day not only for us, but for all of the impacted families."

The Moscow Police Department is leading the investigation into the stabbings, with assistance from the FBI as well as state and local law enforcement agencies.

Officials are next scheduled to hold a news conference Wednesday to update the public on the investigation.

Unknown risk to the public

There are several unanswered questions surrounding the investigation and police have said they have not identified a suspect or found the weapon used in the killings.

The grisly crime rattled the small college community of about 26,000 residents that hasn't recorded a murder since 2015, and anxiety intensified when police said they were unable to ensure the public wasn't at greater risk.

"We cannot say there's no threat to the community and as we have stated, please stay vigilant, report any suspicious activity and be aware of your surroundings at all times," Moscow Police Chief James Fry said Wednesday.

With the community increasingly concerned over the homicides and lack of answers in the case, many students left campus ahead of the fall break.

Some professors canceled classes last week, including Zachary Turpin, who wrote on social media he "can't in good conscience hold class" until police release more information or identify a suspect in the killings.

University of Idaho President Scott Green sent a note to students and employees Monday about learning options. Students are on fall break and when classes resume there will be two weeks left in the semester.

"Faculty have been asked to prepare in-person teaching and remote learning options so that each student can choose their method of engagement ... Moving courses fully online is not preferred but may be necessary in limited situations," he wrote.

Graduation ceremonies are still scheduled for December 10.

He also said an increased number of state troopers will be on campus for the foreseeable future. The size of the school's security force also has been increased, he added.

What authorities know about the attack

Investigators have started to build a timeline of events regarding the students and their last known whereabouts before the fatal attack.

Chapin and Kernodle attended a party at the Sigma Chi fraternity house from 8 p.m. to 9 p.m. Saturday -- the night before they were found dead.

Goncalves and Mogen were at a local sports bar between 10 p.m. and 1:30 a.m. The pair was then seen ordering from a nearby food truck, according to a live Twitch stream from the truck.

As they waited for about 10 minutes for their food, they chatted with each other as well as other people standing by the truck. The man who manages the truck told CNN the pair did not seem to be in distress or in danger in any way.

Goncalves and Mogen used a "private party" for a ride, arriving home at 1:45 a.m., police said. Investigators do not believe the driver was involved in the deaths, they said Saturday. All four victims were back at the house by about 1:45 a.m. Sunday.

From there, authorities are working to determine how and when the attack transpired.

According to Moscow police, it was not until just before noon Sunday when a 911 call was received about an "unconscious individual," and responding officers found the four students dead. Police have said there were no signs of forced entry when officers arrived.

Moscow police "do not believe" two roommates who were at the home during the attack and uninjured were involved in the crime, the department said Friday.

The students were "likely asleep" before being attacked, Moscow police said Friday, citing the Latah County coroner. Some of the four had defensive wounds -- though it is not specified how many victims did -- and there were no signs of sexual assault, according to the police update.

During a news conference Sunday, the police chief declined to identify who placed the 911 call, saying only that it came from the phone of one of the surviving roommates.

Fry said there were other "friends that had arrived at the location," adding that whoever placed the 911 call is not a suspect.

On Monday, police said a dog was also found at the home. "The dog was unharmed and turned over to Animal Services and then released to a responsible party." Moscow Police said in a Facebook post.

The University of Idaho announced a candlelight vigil will be held on campus on November 30 in remembrance of the four students killed.

"Please join us from where you are, individually or as a group, to help us light up Idaho. Light a candle, turn on stadium lights, or hold a moment of silence with us as we unite on campus," the university said.

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CNN's Natasha Chen, Jack Hannah, Paradise Afshar, Ray Sanchez and Travis Caldwell contributed to this report.